Rod lens relay system with reduced chromatic aberration

ABSTRACT

Improved fluoresced imaging (FI) endoscope devices and systems are provided to enhance use of endoscopes with FI and visible light capabilities. An endoscope device is provided for endoscopy imaging in a white light and a fluoresced light mode. A relay system includes an opposing pair of rod lens assemblies positioned symmetrically with respect to a central airspace. The rod lens assemblies include a meniscus lens positioned immediately adjacent to a central airspace and with the convex surface facing the airspace, a first lens having positive power with a convex face positioned adjacent to the inner face of the meniscus lens, a rod lens adjacent to the first lens having positive power and an outer optical manipulating structure selected from various designs providing chromatic aberration correction.

TECHNICAL FIELD OF THE INVENTION

The invention relates generally to the field of medical image captureand more specifically to endoscope designs for improving performancefluorescent imaging and visible light imaging.

BACKGROUND OF THE INVENTION

Endoscopes and other medical scopes often use fluorescing agents orautofluorescence to better examine tissue. A fluorescing agent such as adye may be injected or otherwise administered to tissue. Subsequently,an excitation light is directed toward the tissue. Responsive to theexcitation light, the fluorescing agent fluoresces (emits light,typically at a longer wavelength than the excitation light), allowing asensor to detect this emission light. Image data is collected by thesensor, and examining the collected images can indicate theconcentration of fluorescing agent in the observed tissue. In addition,a phenomenon known as autofluorescence, in which tissue fluoresces undercertain conditions without a fluorescing agent, may occur. Suchautofluorescence can be detected as well. Imaging based on detectedfluoresced light, known as “fluorescence imaging” (FI), is useful inmedical diagnosis, testing, and many scientific fields, and may becombined with visible light imaging for many purposes including toenhance surgical precision.

A typical prior art endoscope 2, as illustrated in FIG. 1 , usuallyincludes a first imaging lens (e.g., an objective) followed by a seriesof carrier lenses (e.g., relays) which capture and transmit an opticalimage from inside an enclosed area 1 to the outside. The proximal end ofthe endoscope 2 may be attached, via direct coupling or an adaptor, to acamera head 3 or an eye-piece for viewing. The camera head 3 usuallyincludes lenses for receiving the optical image and forming a realoptical image onto the image sensor. The digital image captured by theimage sensor can then be transmitted to a camera control unit (CCU) orother similar module for analysis and display.

Frequently, endoscopes used for FI applications, and particularly forapplications involving the dye indocyanine green (ICG) are primarilydesigned and deployed for visible light imagery. As such, they are nottypically designed to maintain a constant focus between infrared lightand visible light. To perform FI imaging, such scopes often employ anappropriate optical filter to block the excitation light and transmitthe fluoresced light. However, as these endoscopes are generallyoptimized for conventional visible light observation, due to theproperties of the optical elements of the scope, including the relaylens system, the infrared fluorescence is focused at a different planethan the visible light, due to chromatic aberration occurring throughoutthe optical system, and primarily in the image relay system. There areexisting approaches to compensate for the resulting focal differences.Camera head solutions include those wherein multiple sensors areemployed, with sensors, associated with particularly wavelength bands(for example one for visible light and one for infrared light) locatedat different focal planes, and directed to the sensors by dichroic beamsplitter. The various spectral bands are detected on the multiplesensors, each an individually appropriate focal plane, resulting in two,independently captured, in-focus images. This approach isdisadvantageous due, only in part, to the complexity and cost of thenecessity for multiple image sensors. Another major concern is that eachindividual endoscope used with such a camera head includes optics whichmay be particular to that make, model and manufacture of scope. Eachparticular endoscope will have varying amounts of chromatic error,requiring any camera head used therewith to compensate specifically forthe error associated with the coupled scope. It is very difficult toconstruct a single camera head capable of compensating for a variety ofendoscope models.

Other efforts to compensate for focal differences, such as, for example,that found in U.S. Pat. No. 8,773,756 to Tesar, et al., involve using anoptical coupler that splits the light into two paths, a visible spectrumpath and a NIR spectrum path. Different optical elements are used ineach of the two beam paths to compensate for the chromatic focaldifferences. However, as with camera head solutions, such systems failto compensate for differences between various endoscopes or tocompensate for the variety of chromatic aberrations across the entiredesired spectrum. For example, there is chromatic aberration, in thesame direction as IR light, in the deep blue range of the visiblespectrum, not addressed by Tesar, resulting in the deep blue range ofthe visible image being not ideally focused at the same plane as theremainder of the visible light. The dispersive properties of the opticalmaterials used in endoscopes, and long glass paths through such opticalmaterials, make conventional correction of the entire spectrum from deepblue to infrared particularly difficult. Finally, the chromaticaberration includes both longitudinal chromatic aberration and lateralchromatic aberration due to obliquely incident light from the objectspace. Techniques that employ lenses or prisms to correct forlongitudinal chromatic aberration often introduce unwanted lateralchromatic aberration.

What is needed are devices and methods to enable endoscope-sidesolutions to issues associated with chromatic aberration of the entirespectrum from deep blue to infrared, such that such an endoscope can beattached to a generic camera head and allow the capture of in-focusvisible light and FI images. What is further needed are endoscopes forfluorescence imaging applications without expensive and slow opticalelements such as autofocus mechanisms or adapters and processing systemsfor chromatic aberration correction.

SUMMARY OF THE INVENTION

It is an object of the invention to improve correction, in endoscopicdevices, of the entire spectrum from deep blue to infrared. In order toachieve this objective, various aspects of the invention provide devicesand systems to enhance endoscopes for use with both FI and visible lightcapabilities. Relay lens systems are disclosed that compensate forchromatic aberration from the deep blue through the infrared spectrumusually utilized in visible and fluorescent imaging in endoscopicprocedures. In particular, relay lens systems are disclosed whichutilize fewer optical elements than has heretofore been possible.Further, some embodiments enable the use of more economical parts thanpossible with other state-of-the-art systems, decreasing cost as well assimplifying construction of both the relay lens systems themselves aswell as the endoscopic devices in which they may be used.

According to a first aspect of the invention, a relay system for anendoscope is provided. The relay system includes an opposing pair of rodlens assemblies positioned symmetrically with respect to a centralairspace, wherein each rod lens assembly includes optical elementsconsisting essentially of a meniscus lens, a first lens, a rod lens, andan outer manipulating structure. The meniscus lens is positionedimmediately adjacent to a central airspace and with the convex surfacefacing the airspace. The first lens has positive power with a convexface positioned adjacent to the inner face of the meniscus lens and isformed of a material having anomalous partial dispersion. The rod lensis adjacent to the first lens having positive power, and has a firstface and a second face, both first and second faces being beam passingfaces. The outer optical manipulating structure is selected from thegroup consisting of: the second face of the rod lens, being concave,positioned adjacent to a second lens having positive power and having aconvex face facing the second concave face of the rod lens; the secondconvex face of the rod lens, being convex, positioned adjacent to anouter meniscus lens; the second face of the rod lens, being plano,positioned adjacent to a plano-convex aspherical lens; the second faceof the rod lens, being plano, positioned adjacent to a positive poweredlens having a convex face facing the second plano face of the rod lenswith a separation gap; the second face of the rod lens, being plano,positioned adjacent to a second plano convex lens; and the second faceof the rod lens, being convex. The meniscus lens, the first lens havingpositive power, the rod lens, and the outer optical manipulatingstructure together provide chromatic aberration correction bymanipulating light from the blue region of the spectrum through the nearIR region of the spectrum to follow the same sequence of opticalsurfaces and come to a common focus in a common image plane.

According to some implementations of first aspect, the first lens havingpositive power is plano-convex.

According to some implementations of first aspect, the first lens ismanufactured from a material having an Abbe number equal to or greaterthan 80.

According to some implementations of first aspect, the outer opticalmanipulating structure is the second, concave face of the rod lenspositioned adjacent to a second lens having positive power and having aconvex face facing the second concave face of the rod lens. In someimplementations, the second lens having positive power may beplano-convex. In some implementations, each rod lens assembly has noadditional optical manipulating elements other than the those listed.

According to some implementations of first aspect, the outer opticalmanipulating structure is the second convex face of the rod lenspositioned adjacent to an outer meniscus lens. In some implementations,each rod lens assembly has no additional optical manipulating elementsother than the those listed.

According to some implementations of first aspect, the outer opticalmanipulating structure is the second plano face of the rod lenspositioned adjacent to a plano-convex aspherical lens. In someimplementations, each rod lens assembly has no additional opticalmanipulating elements other than the those listed.

According to some implementations of first aspect, the outer opticalmanipulating structure is the second plano face of the rod lenspositioned adjacent to a plano-convex lens having a convex face facingthe second plano face of the rod lens with a separation gap. In someimplementations, each rod lens assembly has no additional opticalmanipulating elements other than the those listed.

According to some implementations of first aspect, the outer opticalmanipulating structure is the second plano face of the rod lenspositioned adjacent to a second plano convex lens. In someimplementations, each rod lens assembly has no additional opticalmanipulating elements other than the those listed.

According to some implementations of the first aspect, the outer opticalmanipulating structure is the second convex face of the rod lens. Insome implementations, each rod lens assembly has no additional opticalmanipulating elements other than the those listed.

According to some implementations of the first aspect, the relay systemis also corrected for astigmatism.

According to some implementations of the first aspect, the meniscus lensis constructed of a crown glass having a refractive index less than 1.65and an Abbe number between 55 and 75

According to some implementations of the first aspect, the chromaticaberration correction is provided from approximately 400 nm to 900 nm.

According to some implementations of the first aspect, the pair of rodlens assemblies is arranged around an air space containing an aperturestop.

According to some implementations of the first aspect, the relay systemalso includes an endoscope containing the relay system.

According to some implementations of the first aspect, the first andsecond faces of the rod lens are plano.

According to a second aspect of the invention, a relay system for anendoscope includes an opposing pair of rod lens assemblies positionedsymmetrically with respect a central air space, wherein each rod lensassembly includes a meniscus lens, a first lens, a rod lens, and asingle outer lens. The meniscus lens is positioned adjacent to theopposing rod lens assembly. The first lens has positive optical powerwith a convex face positioned adjacent to an inner face of the meniscuslens. The rod lens positioned adjacent to the first plano-convex lens.The meniscus lens, the first lens having positive optical power, the rodlens, and the single outer lens together are sufficient to manipulatelight to provide chromatic aberration correction by manipulating lightfrom the blue region of the spectrum through the near IR region of thespectrum to follow the same sequence of optical surfaces through therelay system and come to a common focus in a common image plane.

According to some implementations of the second aspect, each rod lensassembly has no additional optical manipulating elements other than thethose listed.

According to some implementations of the second aspect, the first lenshaving positive optical power is manufactured from a material havinganomalous partial dispersion.

According to some implementations of the second aspect, the meniscuslens is constructed of a crown glass having a refractive index less than1.65 and an Abbe number between 55 and 75

According to some implementations of the second aspect, the chromaticaberration correction is provided from approximately 400 nm to 900 nm.

According to some implementations of the second aspect, the relay systemis also corrected for astigmatism.

According to some implementations of the second aspect, the relay systemfurther includes an endoscope containing the relay system.

According to some implementations of the second aspect, the first andsecond faces of the rod lens are plano.

These and other features of the invention will be apparent from thefollowing description of the preferred embodiments, considered alongwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein and the accompanying drawings whichare given by way of illustration only, and thus are not limitative ofthe present invention, and wherein:

FIG. 1 is diagram of a prior art endoscopic system;

FIG. 2 is a block diagram of an endoscope device including a scope andan attached camera head;

FIG. 3 is a partial cross section diagram of the optical relay systemaccording to some embodiments of the invention for use in an endoscopedevice wherein all lenses are spherical, and each rod lens assembly maybe fully cemented together;

FIG. 4 is a chart showing the wavelength versus focal shift achievablewith the optical relay system of FIG. 3 according to an exampleembodiment;

FIG. 5 is a partial cross section diagram of the optical relay system ofthe invention for use in an endoscope device wherein all lenses arespherical, and each rod lens assembly may be fully cemented togetheraccording to additional embodiments;

FIG. 6 is a chart showing the wavelength versus focal shift achievableby the optical relay system of FIG. 5 according to an exampleembodiment;

FIG. 7 is a partial cross section diagram showing an optical relaysystem according to an embodiment where the rod lens element is planaron both ends and the rod lens assembly may be completely cementedtogether;

FIG. 8 is a chart showing the wavelength versus focal shift achievableby the optical relay system of FIG. 7 according to an exampleembodiment;

FIG. 9 is a partial cross section diagram showing an optical relaysystem according to embodiments where the rod lens element is planar onboth ends and all lens elements are spherical, including detachedelements;

FIG. 10 is a chart showing the wavelength versus focal shift achievableby the optical relay system of FIG. 9 according to an exampleembodiment;

FIG. 11 is another chart showing the wavelength versus focal shiftachievable by the optical relay system according to another embodimentof the arrangement of FIG. 9 , using optical elements with differentfocal powers from the embodiment of FIG. 10 ;

FIG. 12 is a partial cross section diagram of an optical relay systemaccording to additional embodiments;

FIG. 13 is a chart showing the wavelength versus focal shift achievableby the optical relay system of FIG. 12 according to an exampleembodiment;

FIG. 14 is another chart showing the wavelength versus focal shiftachievable by the optical relay system according to another embodimentof the arrangement of FIG. 12 using optical elements with differentfocal powers from the embodiment of FIG. 13 .

FIG. 15 is a partial cross section diagram of an optical relay systemaccording to additional embodiments;

FIG. 16 is a chart showing the wavelength versus focal shift achievableby the optical relay system of FIG. 15 according to an exampleembodiment;

FIG. 17 is another chart showing the wavelength versus focal shiftachievable by the optical relay system of FIG. 15 using optical elementswith different focal powers from the embodiment of FIG. 16 ; and

FIG. 18 is a hardware block diagram of system including an example imagecapture device according to an example embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

As used herein, first elements (e.g., sensors and lenses) that are“optically arranged” in relation to other elements, refers to the firstelements' position along a common optical path that includes first andother elements. For example, a lens group optically arranged between animage sensor and an objective, means that the lens group occupies aportion of the optical path that light travels (e.g., from the objectiveto the image sensor) for capturing images or video.

Because digital cameras and FI sensors and related circuitry for signalcapture and processing are well-known, the present description will bedirected in particular to elements forming part of, or cooperating moredirectly with, a method and apparatus in accordance with the invention.Elements not specifically shown or described herein are selected fromthose known in the art. Certain aspects of the embodiments to bedescribed are provided in software. Given the system as shown anddescribed according to the invention in the following materials,software not specifically shown, described or suggested herein that isuseful for implementation of the invention is conventional and withinthe ordinary skill in such arts.

FIG. 2 is a block diagram of an endoscope device 100 according to anexample embodiment of the invention. Endoscope device 100 (“device 100”,“endoscope 100”) includes a shaft 102 connected to a proximal element101. The proximal element 101 may be an eyecup including an eyepieceenabling the user to view visible light traversing the shaft 102. Theeyecup may also act as an attachment element to connect the scope to acamera head 216 containing one more image sensors, via a bayonetconnection, or other connection system known in the art. Alternativelythe camera head element may be integrated with the shaft via theproximal element 101. Various structural components supporting thedepicted elements are omitted in the diagrams herein, as well as othercomponents such as illumination sources, fluorescent excitation sources,and controls which are known in the art and are not shown in order toavoid obscuring the relevant details of the example embodiments of theinvention. At the left is shown the distal tip of the endoscope shaft102 including a cover glass 202, which in this version faces directlyalong the longitudinal axis of the shaft 102, but may also be positionedat an angle relative to the longitudinal axis as is known in the art.Behind, or on the proximal side of, the cover glass 202 is shown apreferred position for the objective lens 204, usually set against orvery near cover glass 202 and preferably assembled together with thecover glass in construction. While a wide angle lens is preferred forobjective lens 204, this is not limiting, and any suitable lens may beused in various embodiments. Objective lens 204 may be part of anobjective lens group 104 which may include one or more additional lenses103. The particular number and arrangement of lenses in the endoscopeshaft 102 will vary widely depending on the application. Opticallyarranged or attached at the proximal side of objective lens 204 orobjective lens group 104 is rod lens relay system 107, which serves topass the light down shaft 102 in the proximal direction. Rod lens relaysystem 107, including rod lens pairs, is adapted to direct the imagelight to create a telecentric internal image space at the proximal endof the one or more rod lenses, where a second lens group 214 ispositioned as further discussed below. Also, the shaft 102 is typicallyrigid but shaft design variations are also known to allow rod lenses tobe used in a semi-flexible shaft in which flexible joints are present inone or more places along the shaft between the rod lenses, while theshaft is rigid along the portions containing a rod lens. Such a shaftdesign may be used in various embodiments of the invention.

Rod lens relay system 107 functions to compensate for the chromaticaberration of the endoscope's multiple lenses such that a first portionof light having a first wavelength spectrum and a second portion oflight having a second wavelength spectrum different from the first arefocused onto substantially the same image plane. Assembly 214 ispositioned within a telecentric internal image space proximal to rodlens relay system 107. Second lens group 214 is preferably positionedwithin the proximal element 101 of device 100, but may partially spanthe volume of the shaft 102 and the proximal element 101 or may be anelement of the camera head or eyepiece 216.

Typically, rod lens relay system 107 is integrated with endoscope device100, and, in particular, the shaft 102, and is designed to correct forchromatic aberrations. As further described below, some embodiments alsoprovide astigmatism correction. The eyepiece, or the image sensorassembly and its associated electronics (together constituting a camera)may be integrated with the device or may be separate and detachable,such as a detachable eyepiece or a detachable camera head. In variousembodiments the invention may therefore constitute an endoscopic deviceor an imaging system including an endoscopic device 100.

FIG. 3 is a partial cross section diagram of an optical relay lenssystem 300 according to some embodiments to be used in an endoscopedevice 100. The depicted relay system 300 may be employed, for example,as rod lens relay system 107 in the system of FIG. 2 . Relay system 300includes an opposing pair of rod lens assemblies 301 positionedsymmetrically with respect to a central airspace. More than one suchpair may be employed in series to provide an overall relay system with agreater length. The central airspace between rod lens assemblies 301 maycontain an aperture stop. This embodiment has the advantages ofconsisting of only four optical elements per rod lens assembly, whereineach lens is spherical, and the rod lens assembly may be fully cementedtogether and may have a planar outer surface, which can simplify thedesign and assembly of the overall relay system within the shaft 102.

Each rod lens assembly 301, according to this embodiment, includes ameniscus lens 302 positioned adjacent to the opposing rod lens assembly.A first plano-convex lens 304 has a convex face positioned adjacent toan inner face of meniscus lens 302 and a planar face at the oppositeside. Other lenses may be used instead of a plano-convex lens. A rodlens 306 has a first plano surface positioned adjacent to the plano faceof first plano-convex lens 304.

At the opposing, outer end of rod lens 306 is an outer opticalmanipulating structure which in this embodiment includes a secondconcave face of rod lens 306 positioned adjacent to a secondplano-convex lens 308 having a convex face facing the second concaveface of rod lens 306.

A light ray diagram is shown showing the path taken by light 310 passingfrom an object plane depicted on the left to an image plane depicted onthe right. Meniscus lens 302, first plano-convex lens 304, rod lens 306,and the outer optical manipulating structure together perform chromaticaberration correction by manipulating light 310 of a spectrum from theblue region through the near IR region to have substantially the sameeffective optical path length and thus come to a common focus at acommon image plane, allowing for simultaneous imaging throughout thespectrum. Each rod lens assembly 301 has no additional opticalmanipulating elements other than the those listed which together providea chromatic aberration correction sufficient to allow simultaneousimaging of visible and IR spectrum light at the depicted common imagingplane, or sequential or separate imaging without refocusing adjustmentsfor the visible and IR spectra. The amount of chromatic aberrationcorrection may vary depending on the materials, sizes, and curvatures ofthe various optical manipulating elements. Depending on the f-number ofthe system, the amount of correction in focal position due to chromaticaberration sufficient to allow simultaneous imaging across the IR andvisible spectrum may be less than about 15 micrometers shift across thespectral range of 400 nm to 900 nm. Additionally, depending on thenumber of relays in a system, this correction in focal position mayvary, as associated errors accumulate over multiple relays. Morepreferably, a correction to a total aberration of 10 micrometers offocal shift across that range is achievable with certain embodimentsemploying the relay system of FIG. 3 .

Meniscus lens 302 is preferably constructed with a crown glass having arefractive index less than 1.65 and an Abbe number between 55 and 75.Preferably, the first positive power lens 304, which is typically aplano-convex lens but may be another positive power lens, is constructedof a material having anomalous partial dispersion. The material of thefirst positive power lens 304 preferably has a lower refractive indexand higher Abbe number than the material of the rod lens. For example,various types of crown glass may be used such as phosphate glasses orfluorophosphate glasses. A relatively high Abbe number is preferablyused such as 55 or over. For example, various versions may employ crownglass with an Abbe number of 65, 70, 75, 80, or 85. For example, firstpositive power lens 304 has an Abbe number of 81.54 in some embodiments.Optical properties of the surface elements of one possibleimplementation of the embodiment shown in FIG. 3 are given in Table 1.

TABLE 1 Surface Data Summary for one implementation of the embodimentFIG. 3 Surface Radius Thickness Index Abbe no. Clear Diam Obj Infinity3.302 Air 4.20 1 Infinity 2.0 1.847 23.78 6.48 2 −7.2169 43.532 1.61849.82 6.48 3 Infinity 2.5 1.497 81.55 6.48 4 −6.0591 1.4 1.522 59.486.48 5 −15.8891  0.25 Air 6.48 STO Infinity 0.25 Air 4.5857 7 15.88911.4 1.522 59.48 6.48 8  6.0591 2.5 1.497 81.55 6.48 9 Infinity 43.5321.618 49.82 6.48 10   7.2169 2.0 1.847 23.78 6.48 11  Infinity 3.302 Air6.48 IMA Infinity 4.2217

In this embodiment, as well as the embodiments described below withrespect to FIG. 5 , FIG. 7 , and FIG. 9 , the relay system also providescorrection for astigmatism. As endoscope systems with rod lenses oftenhave astigmatism, the outer optical manipulating structure of theseembodiments preferably performs an astigmatism correction function.

FIG. 4 is a chart showing chromatic aberration correction achievablewith the relay system of FIG. 3 according to an example implementationwith the properties shown in Table 1. The vertical axis shows the lightwavelength in micrometers from 0.4 to 0.9 (400 to 900 nanometers), andthe horizontal axis shows the focal shift provided by the relay systemusing a single pair of rod lens assemblies 301 in an endoscope opticalassembly. As can be seen on the chart, the focal shift is about 6micrometers at the 405 nanometer wavelength and exhibits a curve toabout negative 4 micrometers of focal shift at the 900 nanometerwavelength, for a total focal shift range of about 10 micrometers acrossthe depicted spectrum. This focal shift provided by the inventiveoptical relay system minimizes the variance of focal position as afunction of wavelength which would ordinarily be present due tochromatic aberration of a conventional rod lens relay pair.

FIG. 5 is a partial cross section diagram of an optical relay lenssystem 500 according to some additional embodiments to be used in anendoscope device 100. A light ray diagram is overlaid on the diagram.Relay system 500 includes an opposing pair of rod lens assemblies 501positioned symmetrically with respect to a central airspace. As with theembodiments of FIG. 3 , more than one such pair may be employed inseries to provide an overall relay system with a greater length. Thecentral airspace between rod lens assemblies 501 may contain an aperturestop. This embodiment has the advantages of consisting of only fouroptical elements per rod lens assembly, wherein each lens is spherical,and the rod lens assembly may be fully cemented together, which cansimplify the design and assembly of the overall relay system within theshaft 102.

Each rod lens assembly 501 includes a meniscus lens 302 and a firstplano-convex lens 304, or other positive power lens, similar to thosedescribed with respect to FIG. 3 . In this embodiment, a rod lens 506 isa plano-convex rod lens having has a first plano surface positionedadjacent to the plano face of first plano-convex lens 304. At theopposing, outer end of rod lens 506 is an outer optical manipulatingstructure which includes a second convex face of rod lens 506 positionedadjacent to an outer meniscus lens 508.

Meniscus lens 302, first plano-convex lens 304, rod lens 506, and theouter optical manipulating structure together perform chromaticaberration correction by manipulating light 510 in the blue region ofthe spectrum through the near IR region of the spectrum to have the sameeffective optical path length so as to come to a common focus at acommon image plane. Each rod lens assembly 501 has no additional opticalmanipulating elements other than the those listed which together providea chromatic aberration correction sufficient to allow simultaneousimaging of visible and IR spectrum light at the depicted common imagingplane, or sequential or separate imaging without refocusing adjustmentsfor the visible spectrum and IR. Optical properties of the surfaceelements of an implementation of the embodiment shown in FIG. 5 aregiven in Table 2.

TABLE 2 Surface Data Summary for one implementation of the embodimentshown in FIG. 5 Surface Radius Thickness Index Abbe no. Clear Diam ObjInfinity 6.0 Air 4.2 1  13.2864 2.0 1.847 23.78 6.48 2  6.5539 44.8351.618 49.82 6.48 3 Infinity 2.5 1.497 81.55 6.48 4  −5.8150 1.4 1.51270.86 6.48 5 −17.8746 0.25 Air 6.48 STO Infinity 0.25 Air 5.3157 7 17.8746 1.4 1.512 70.86 6.48 8  5.8150 2.5 1.497 81.55 6.48 9 Infinity44.835 1.618 49.82 6.48 10   −6.5539 2.0 1.847 23.78 6.48 11  −13.28646.0 Air 6.48 IMA Infinity 4.2209

FIG. 6 is a chart showing chromatic aberration correction achievablewith the relay system of FIG. 5 according to an example implementationwith the properties shown in Table 2. As can be seen, the range of focalshift across the spectrum from 405 to 900 nanometers varies from a minus8 micrometer shift to about 5 micrometers, for a total range ofapproximately 13 micrometers. This focal shift provided by the inventiveoptical relay system minimizes the variance of focal position as afunction of wavelength which would ordinarily be present due tochromatic aberration of a conventional rod lens relay pair.

FIG. 7 is a partial cross section diagram of an optical relay lenssystem 700 according to additional embodiments to be used in anendoscope device 100. In this embodiment, and that of FIG. 9 , the rodlenses 706 are plano-plano rod lenses which provide lower constructioncosts compared to rod lenses having curved faces. Relay system 700includes an opposing pair of rod lens assemblies 701 positionedsymmetrically with respect to a central airspace. As with theembodiments of FIG. 3 , more than one such pair may be employed inseries to provide an overall relay system with a greater length. Thecentral airspace between rod lens assemblies 301 may contain an aperturestop. This embodiment has the advantages, beyond that of theplanar-planar rod lens element, of consisting of only four opticalelements per rod lens assembly and the rod lens assembly may be fullycemented together, which can simplify the design and assembly of theoverall relay system within the shaft 102.

A light ray diagram is overlaid on the diagram showing light passingfrom the object plane depicted on the left to an image plane depicted onthe right. As with the other embodiments herein, additional pairs rodlens assemblies 701 may be placed end to end with the depicted pair ofassemblies, with the image plane at which an image is measured with asensor positioned after the final pair of rod lens assemblies.

Each rod lens assembly 701 includes a meniscus lens 302 and a firstplano-convex lens 304, or other positive power lens, similar to thosedescribed with respect to FIG. 3 . In this embodiment, a rod lens 706 isa plano-plano rod lens having has a first plano surface positionedadjacent to the plano face of first plano-convex lens 304. At theopposing, outer end of rod lens 706 is an outer optical manipulatingstructure which includes a second plano face of rod lens 706 positionedadjacent to a plano-convex aspherical lens 708. The use of an asphericlens in this embodiment provides ability to correct for astigmatismwhile using a lower cost plano-plano rod lens.

Meniscus lens 302, first plano-convex lens 304, rod lens 706, and theouter optical manipulating structure together perform chromaticaberration correction by manipulating light 710 in the blue region ofthe spectrum through the near IR region of the spectrum to have the sameeffective optical path length, and thus come to a common focus at acommon image plane. Each rod lens assembly 701 has no additional opticalmanipulating elements other than the those listed which together providea chromatic aberration correction sufficient to allow simultaneousimaging of visible and IR spectrum light at the depicted common imagingplane, or sequential or separate imaging without refocusing adjustmentsfor the visible spectrum and IR. Optical properties of the surfaceelements of an implementation of the embodiment shown in FIG. 7 aregiven in Table 3.

TABLE 3 Surface Data Summary for one implementation of the embodimentshown in FIG. 7 Abbe Clear Surface Radius Thickness Index no. Diam ConicObj Infinity 6.995 Air 4.2 0 1 20.8646 2.0 1.717 29.52 6.48 −5.6347 2Infinity 41.805 1.618 49.82 6.48 0 3 Infinity 2.5 1.529 76.98 6.48 0 4−5.5174  1.4 1.540 59.71 6.48 0 5 −19.4448   0.3 Air 6.48 0 STO Infinity0.3 Air 4.5372 0 7 19.4448 1.4 1.540 59.71 6.48 8  5.5174 2.5 1.52976.98 6.48 0 9 Infinity 41.805 1.618 49.82 6.48 0 10  Infinity 2.0 1.71729.52 6.48 0 11  −20.8646   6.995 Air 6.48 −5.6347 IMA Infinity 4.2247 0

FIG. 8 is a chart showing chromatic aberration correction achievablewith the relay system of FIG. 7 according to an example implementationwith the properties shown in Table 3. The focal shift ranges fromslightly larger than negative 8 micrometers at the 405 nanometerwavelength, to about positive 3 micrometers around 700 nanometers,providing a total focal shift range of about 11 micrometers. This focalshift provided by the inventive optical relay system minimizes thevariance of focal position as a function of wavelength which wouldordinarily be present due to chromatic aberration of a conventional rodlens relay pair.

FIG. 9 is a partial cross section diagram of an optical relay lenssystem 900 according to additional embodiments to be used in anendoscope device 100. Relay system 900 includes an opposing pair of rodlens assemblies 901 positioned symmetrically with respect to a centralairspace. As with the embodiments discussed above, more than one suchpair may be employed in series to provide an overall relay system with agreater length. The central airspace between rod lens assemblies 301 maycontain an aperture stop. This embodiment has the advantages, beyondthat of the planar-planar rod lens element, of consisting of only fouroptical elements per rod lens assembly and all of the lenses arespherical.

A light ray diagram is overlaid on the diagram showing light passingfrom the object plane depicted on the left to an image plane depicted onthe right. Additional pairs rod lens assemblies 901 may be placed end toend with the depicted pair of assemblies, with the image plane at whichan image is measured with a sensor positioned after the final pair ofrod lens assemblies.

Each rod lens assembly 901 includes a meniscus lens 302 and a firstplano-convex lens 304, or other positive power lens, like those of FIG.3 . In this embodiment, a rod lens 906 is a plano-plano rod lens havinghas a first plano surface positioned adjacent to the plano face of firstplano-convex lens 304. At the opposing, outer end of rod lens 906 is anouter optical manipulating structure which includes a second plano faceof the rod lens positioned adjacent to a plano-convex lens 908 having aconvex face facing the second plano face of the rod lens with aseparation gap. Other lenses with a positive power may be used in placeof plano-convex lens 908. This embodiment also provides ability tocorrect for astigmatism while using a low cost plano-plano rod lens inthe relay system.

Meniscus lens 302, first plano-convex lens 304, rod lens 906, and theouter optical manipulating structure 908 together perform chromaticaberration correction by manipulating light 910 in the blue region ofthe spectrum through the near IR region of the spectrum to have the sameeffective optical path length, and thus and come to a common focus at acommon image plane. Each rod lens assembly 901 has no additional opticalmanipulating elements other than the those listed which together providea chromatic aberration correction sufficient to allow simultaneousimaging of visible and IR spectrum light at the depicted common imagingplane, or sequential or separate imaging without refocusing adjustmentsfor the visible spectrum and IR. Optical properties of the surfaceelements of an implementation of the embodiment shown in FIG. 9 aregiven in Table 4.

TABLE 4 Surface data summary for one implementation of the embodimentshown in FIG. 9 Surface Radius Thickness Index Abbe no. Clear Diam ObjInfinity 4.553 Air 4.2 1 Infinity 2.0 1.923 18.90 6.48 2 −27.8072 2.284Air 6.48 3 Infinity 39.966 1.618 49.82 6.48 4 Infinity 2.5 1.497 81.556.48 5  −6.2398 1.4 1.523 59.48 6.48 6 −16.6953 0.25 Air 6.48 STOInfinity 0.25 Air 4.5853 8  16.6953 1.4 1.523 59.48 6.48 9  6.2398 2.51.497 81.55 6.48 10 Infinity 39.996 1.618 49.82 6.48 11 Infinity 2.284Air 6.48 12  27.8073 2.0 1.923 18.90 6.48 13 Infinity 4.553 Air 6.48 IMAInfinity 4.2233

FIG. 10 is a chart showing chromatic aberration correction achievablewith the relay system of FIG. 9 according to an example implementationwith the properties shown in Table 3. The focal shift ranges from 12micrometers at the 405 nanometer wavelength, to slightly under zeromicrometers at 550 nanometers, providing a total focal shift range ofabout 12 micrometers.

FIG. 11 is another chart showing chromatic aberration achievableaccording to another implementation of the embodiment of FIG. 9 usingelements with different properties (shown in Table 5) from theembodiment of FIG. 10 . In this version, the focal shift ranges fromabout negative 4 micrometers at 405 nanometers, to slightly over twomicrometers at 900 nanometers, for a total focal shift range of slightlyover 6 micrometers. This focal shift provided by the inventive opticalrelay system minimizes the variance of focal position as a function ofwavelength which would ordinarily be present due to chromatic aberrationof a conventional rod lens relay pair.

TABLE 5 Alternative surface data summary for one implementation of theembodiment shown in FIG. 9 Surface Radius Thickness Index Abbe no. ClearDiam Obj Infinity 6.3133 Air 4.2 1 102.5046 2.0 1.923 18.90 6.48 2−34.8825 0.25 Air 6.48 3 Infinity 40.2717 1.620 36.37 6.48 4 Infinity2.5 1.497 81.55 6.48 5  −6.2200 1.4 1.522 59.48 6.48 6 −17.0677 0.25 Air6.48 STO Infinity 0.25 Air 4.3345 8  17.0677 1.4 1.522 59.48 6.48 9 6.2200 2.5 1.497 81.55 6.48 10 Infinity 40.2717 1.620 36.37 6.48 11Infinity 0.25 Air 6.48 12  34.8825 2.0 1.923 18.90 6.48 13 −102.5046 6.3133 Air 6.48 IMA Infinity 4.2

FIG. 12 is a partial cross section diagram of an optical relay lenssystem 1200 according to additional embodiments to be used in anendoscope device 100. Relay system 1200 includes an opposing pair of rodlens assemblies 1201 positioned symmetrically with respect to a centralairspace. As with the embodiments discussed above, more than one suchpair may be employed in series to provide an overall relay system with agreater length. The central airspace between rod lens assemblies 1201may contain an aperture stop. While, as opposed to the embodiments shownabove, this embodiment does not explicitly correct for astigmatism, itoffers a simplified design, employing a plano-plano rod lens, consistsof only four optical elements per rod lens assembly, and all of thelenses are spherical and may be cemented together into a single unit.

A light ray diagram is overlaid on the diagram showing light passingfrom the object plane depicted on the left to an image plane depicted onthe right. Additional pairs rod lens assemblies 1201 may be placed endto end with the depicted pair of assemblies, with the image plane atwhich an image is measured with a sensor positioned after the final pairof rod lens assemblies.

Each rod lens assembly 1201 includes a meniscus lens 302 and a positivepower lens such as first plano-convex lens 304 like that of FIG. 3 . Inthis embodiment, a rod lens 1206 is a plano-plano rod lens having has afirst plano surface positioned adjacent to the plano face of firstplano-convex lens 304. At the opposing, outer end of rod lens 1206 is anouter optical manipulating structure which includes a second plano faceof the rod lens positioned adjacent to a plano-convex lens 1208 having aplano face adjacent to rod lens 1206 and a convex face directed outward.

Meniscus lens 302, first plano-convex lens 304, rod lens 1206, and theouter optical manipulating structure together perform chromaticaberration correction by manipulating light 1210 in the blue region ofthe spectrum through the near IR region of the spectrum to havesubstantially the same effective optical path length, and therefore cometo a common focus at a common image plane. Each rod lens assembly 1201has no additional optical manipulating elements other than the thoselisted which together provide a chromatic aberration correctionsufficient to allow simultaneous imaging of visible and IR spectrumlight at the depicted common imaging plane, or separate or sequentialimaging without refocusing adjustments for the visible spectrum and IR.

FIGS. 13 and 14 are charts showing chromatic aberration correctionachievable with implementations of the relay system of FIG. 12 . FIG. 13, with corresponding surface properties given in Table 6, shows a focalshift range from about negative 9 micrometers at the 405 nanometerwavelength, to about 3 micrometers at 700 nanometers, providing a totalfocal shift range of about 12 micrometers. FIG. 14 , with correspondingsurface properties given in Table 7, shows a focal shift rang from about14 micrometers at 405 nanometers, to about negative two micrometers ataround 500 nanometers, for a total focal shift range of 16 micrometers.This focal shift provided by the inventive optical relay systemminimizes the variance of focal position as a function of wavelengthwhich would ordinarily be present due to chromatic aberration of aconventional rod lens relay pair.

TABLE 6 Surface Data Summary for one implementation of the embodimentshown in FIG. 12 Surface Radius Thickness Index Abbe no. Clear Diam ObjInfinity 7.257 Air 4.2 1 21.3368 2.0 1.717 29.52 6.48 2 Infinity 41.5431.618 49.82 6.48 3 Infinity 2.5 1.529 76.98 6.48 4 −5.4641 1.4 1.54059.71 6.48 5 −19.5366 0.3 Air 6.48 STO Infinity 0.3 Air 4.5429 7 19.53661.4 1.540 59.71 6.48 8 5.4641 2.5 1.529 76.98 6.48 9 Infinity 41.5431.618 49.82 6.48 10  Infinity 2.0 1.718 29.52 6.48 11  −21.3368 7.257Air 6.48 IMA Infinity 4.2695

TABLE 7 Surface Data Summary for an alternative implementation of theembodiment shown in FIG. 12 Surface Radius Thickness Index Abbe no.Clear Diam Obj Infinity 4.716 Air 4.2 1  25.0813 2.0 1.801 34.97 6.48 2Infinity 44.083 1.618 49.82 6.48 3 Infinity 2.5 1.439 94.66 6.48 4 −7.6413 1.4 1.569 63.10 6.48 5 −13.1283 0.3 Air 6.48 STO Infinity 0.3Air 4.8458 7  13.1283 1.4 1.569 63.10 6.48 8  7.6413 2.5 1.439 94.666.48 9 Infinity 44.083 1.618 49.82 6.48 10  Infinity 2.0 1.801 34.976.48 11  −25.0813 4.716 Air 6.48 IMA Infinity 4.2545

FIG. 15 is a partial cross section diagram of an optical relay lenssystem 1500 according to additional embodiments to be used in anendoscope device 100. Relay system 1500 includes an opposing pair of rodlens assemblies 1501 positioned symmetrically with respect to a centralairspace. As with the embodiments discussed above, more than one suchpair may be employed in series to provide an overall relay system with agreater length. As with the embodiment shown in FIG. 12 , thisembodiment does not explicitly correct for astigmatism, however itoffers a simplified design, employing only three optical elements perrod lens assembly, and all of the lenses may be cemented together into asingle unit.

A light ray diagram is overlaid on the diagram showing light passingfrom the object plane depicted on the left to an image plane depicted onthe right. Additional pairs rod lens assemblies 1501 may be placed endto end with the depicted pair of assemblies, with the image plane atwhich an image is measured with a sensor positioned after the final pairof rod lens assemblies.

Each rod lens assembly 1501 includes a meniscus lens 302 and a positivepower lens such as first plano-convex lens 304 like that of FIG. 3 . Inthis embodiment, a rod lens 1506 is a plano-convex rod lens having has afirst plano surface positioned adjacent to the plano face of firstplano-convex lens 304. At the opposing, outer end of rod lens 1506 is anouter optical manipulating structure which includes a convex face of therod lens directed outward.

Meniscus lens 302, first plano-convex lens 304, rod lens 1506, and theouter optical manipulating structure together perform chromaticaberration correction by manipulating light 1510 in the blue region ofthe spectrum through the near IR region of the spectrum to have the sameeffective optical path length, and thus come to a common focus at acommon image plane. Each rod lens assembly 1501 has no additionaloptical manipulating elements other than the those listed which togetherprovide a chromatic aberration correction sufficient to allowsimultaneous imaging of visible and IR spectrum light at the depictedcommon imaging plane, or separate or sequential imaging withoutrefocusing adjustments for the visible spectrum and IR.

FIGS. 16 and 17 are charts showing chromatic aberration correctionachievable with implementations of the relay system of FIG. 15 . FIG. 16, with corresponding surface properties given in Table 8 shows a focalshift range from about negative 7 micrometers at the 475 nanometerwavelength, to about 3 micrometers at 900 nanometers, providing a totalfocal shift range of about 10 micrometers. FIG. 17 , with correspondingsurface properties given in Table 9, shows a focal shift range fromabout negative 10 micrometers at 475 nanometers, to about threemicrometers at around 725 nanometers, for a total focal shift range of13 micrometers. This focal shift provided by the inventive optical relaysystem minimizes the variance of focal position as a function ofwavelength which would ordinarily be present due to chromatic aberrationof a conventional rod lens relay pair.

TABLE 8 Surface Data Summary for one implementation of the embodimentshown in FIG. 15 Surface Radius Thickness Index Abbe no. Clear Diam ObjInfinity 6.0 Air 4.2 1  23.0368 55.533 1.618 49.82 6.48 2 Infinity 2.51.497 81.55 6.48 3  −6.6931 1.4 1.512 64.98 6.48 4 −20.6228 0.25 Air6.48 STO Infinity 0.25 Air 5.7193 6  20.6228 1.4 1.512 64.98 6.48 7 6.6931 2.5 1.497 81.55 6.48 8 Infinity 55.533 1.618 49.82 6.48 9−23.0368 6.0 Air 6.48 IMA Infinity 4.2557

TABLE 9 Surface Data Summary for one implementation of the embodimentshown in FIG. 15 Surface Radius Thickness Index Abbe no. Clear Diam ObjInfinity 6.0 Air 4.2 1  18.2447 42.835 1.620 36.37 6.48 2 Infinity 2.51.497 81.55 6.48 3  −6.2847 1.4 1.525 64.67 6.48 4 −16.6115 0.25 Air6.48 STO Infinity 0.25 Air 4.5273 6  16.6115 1.4 1.525 64.67 6.48 7 6.2847 2.5 1.497 81.55 6.48 8 Infinity 42.835 1.620 36.37 6.48 9−18.2447 6.0 Air 6.48 IMA Infinity 4.2720

Referring to FIG. 18 , a block diagram of system including an imagecapture device and an endoscope device having an improved correction ofchromatic aberration as described above. The invention is applicable tomore than one type of device enabled for image capture, such asFI-capable endoscopes, other FI medical imaging devices. The preferredversion is an imaging scope system, such as an endoscope.

As shown in the diagram of an endoscope device system, a light source 8illuminates subject scene 9 with visible light and/or fluorescentexcitation light, which may be outside the visible spectrum in theultra-violet range or the infra-red/near infrared range, or both. Lightsource 8 may include a single light emitting element configured toprovide light throughout the desired spectrum, or a visible lightemitting element and a one or more fluorescent excitation light emittingelements. Further, light source 8 may include fiber optics passingthrough the body of the scope, or other light emitting arrangements suchas LEDs or laser diodes positioned at or near the front of the scope.

As shown in the drawing, light 10 reflected from (or, alternatively, asin the case of fluorescence, excitation light 8 absorbed andsubsequently emitted by) the subject scene is input to an opticalassembly 11, where the light is focused to form an image at asolid-state image sensor(s) 222 and/or fluoresced light sensor(s) 223.

Optical assembly 11 includes an optical relay system constructedaccording to the techniques provided herein. For example, theembodiments of FIG. 3 , FIG. 5 , FIG. 7, FIG. 9 , FIG. 12 , or FIG. 15may be used, or other embodiments. An additional lens group may beincluded at the camera head, as discussed with respect to FIG. 2 . Asdiscussed above, portions of the optical assembly may be embodied in acamera head or other first optical device, while other portions are inan endoscope or other scope device, or the optical assembly 11 may becontained in a single imaging device. Image sensor 222 (which mayinclude separate R, G, and B sensor arrays) and fluoresced light sensor223 convert the incident visible and invisible light to an electricalsignal by integrating charge for each picture element (pixel). It isnoted that fluoresced light sensor 223 is shown as an optional dottedbox because embodiments may use the RGB image sensor 222 to detect onlywhite light images or to also detect fluoresced light (e.g., NIR, ICG,FI). The latter scheme may be used when the fluoresced light is in aspectrum detectable by image sensor 222 that is in or near the visiblelight spectrum typically detected by a RGB sensor arrays.

Of course, alternate implementations of the present inventive relay lenssystems are possible. For example, optical assembly 11 may include adichroic beam splitting element and may direct one band of the spectrato one sensor for visual imaging and another band to another sensor forfluorescence imaging. As the present invention enables a scope sidesolution to the problems associated with chromatic aberration in relaysystems, the camera head image sensor assembly 28 need not be adjustedto assure both visible and FI images are in focus.

The image sensor 222 and fluoresced light sensor 223 may be active pixelcomplementary metal oxide semiconductor sensor (CMOS APS) or acharge-coupled device (CCD).

The total amount of light 10 reaching the image sensor 222 and/orfluoresced light sensor 223 is regulated by the light source 8intensity, the optical assembly 11 aperture, and the time for which theimage sensor 222 and fluoresced light sensor 223 integrates charge. Anexposure controller 40 responds to the amount of light available in thescene given the intensity and spatial distribution of digitized signalscorresponding to the intensity and spatial distribution of the lightfocused on image sensor 222 and fluoresced light sensor 223.

Exposure controller 40 also controls the emission of fluorescentexcitation light from light source 8, and may control the visible andfluorescent light emitting elements to be on at the same time, or toalternate to allow fluoresced light frames to be captured in the absenceof visible light if such is required by the fluorescent imaging schemeemployed. Exposure controller 40 may also control the optical assembly11 aperture, and indirectly, the time for which the image sensor 222 andfluoresced light sensor 223 integrate charge. The control connectionfrom exposure controller 40 to timing generator 26 is shown as a dottedline because the control is typically indirect.

Typically, exposure controller 40 has a different timing and exposurescheme for each of sensors 222 and 223. Due to the different types ofsensed data, the exposure controller 40 may control the integration timeof the sensors 222 and 223 by integrating sensor 222 up to the maximumallowed within a fixed 60 Hz or 50 Hz frame rate (standard frame ratesfor USA versus European video, respectively), while the fluoresced lightsensor 223 may be controlled to vary its integration time from a smallfraction of sensor 222 frame time to many multiples of sensor 222 frametime. The frame rate of sensor 222 will typically govern thesynchronization process such that images frames based on sensor 223 arerepeated or interpolated to synchronize in time with the 50 or 60 fpsrate of sensor 222.

Analog signals from the image sensor 222 and fluoresced light sensor 223are processed by analog signal processor 22 and applied toanalog-to-digital (A/D) converter 24 for digitizing the analog sensorsignals. The digitized signals each representing streams of images orimage representations based on the data, are fed to image processor 30as image signal 27, and first fluorescent light signal 29. For versionsin which the image sensor 222 also functions to detect the fluorescedlight, fluoresced light data is included in the image signal 27,typically in one or more of the three color channels.

Image processing circuitry 30 includes circuitry performing digitalimage processing functions to process and filter the received images asis known in the art. Image processing circuitry may include separate,parallel pipelines for processing the visible light image data and theFI image data separately. Such circuitry is known in the art and willnot be further described here.

Image processing circuitry 30 may provide algorithms, known in the art,for combining visible light imagery with FI imagery in a combined imagedisplay, and further highlighting or emphasizing the FI imagery foreasily distinguishing the presence of fluorescing features in the image.

Timing generator 26 produces various clocking signals to select rows andpixels and synchronizes the operation of image sensor 222 andfluorescent sensor 223, analog signal processor 22, and A/D converter24. Image sensor assembly 28 includes the image sensor 222 andfluorescent sensor 223, adjustment control 20, the analog signalprocessor 22, the A/D converter 24, and the timing generator 26. Thefunctional elements of the image sensor assembly 28 can be fabricated asa single integrated circuit as is commonly done with CMOS image sensorsor they can be separately-fabricated integrated circuits.

The system controller 50 controls the overall operation of the imagecapture device based on a software program stored in program memory 54.This memory can also be used to store user setting selections and otherdata to be preserved when the camera is turned off.

System controller 50 controls the sequence of data capture by directingexposure controller 40 to set the light source 8 intensity, the opticalassembly 11 aperture, and controlling various filters in opticalassembly 11 and timing that may be necessary to obtain image streamsbased on the visible light and fluoresced light. In some versions,optical assembly 11 includes an optical filter configured to attenuateexcitation light and transmit the fluoresced light. A data bus 52includes a pathway for address, data, and control signals.

Processed image data are continuously sent to video encoder 80 toproduce a video signal. This signal is processed by display controller82 and presented on image display 88. This display is typically a liquidcrystal display backlit with light-emitting diodes (LED LCD), althoughother types of displays are used as well. The processed image data canalso be stored in system memory 56 or other internal or external memorydevice.

The user interface 60, including all or any combination of image display88, user inputs 64, and status display 62, is controlled by acombination of software programs executed on system controller 50. Userinputs typically include some combination of typing keyboards, computerpointing devices, buttons, rocker switches, joysticks, rotary dials, ortouch screens. The system controller 50 manages the graphical userinterface (GUI) presented on one or more of the displays (e.g. on imagedisplay 88). In particular, the system controller 50 will typically havea mode toggle user input (typically through a button on the endoscope orcamera head itself, but possibly through a GUI interface), and inresponse transmit commands to adjust image processing circuitry 30 basedon predetermined setting stored in system memory. Preferably a systememployed with any of the device designs herein provides ability totoggle between at least two modes, visible light and FI modes, and morepreferably a combined mode is included in which FI images are combinedor overlaid with visible images in a suitable manner known in the art.Such settings may include different settings for different models ofscopes that may be attached to a camera head or other imaging devicecontaining image sensor assembly 28.

Image processing circuitry 30 is one of three programmable logicdevices, processors, or controllers in this embodiment, in addition to asystem controller 50 and the exposure controller 40. Image processingcircuitry 30, controller 50, exposure controller 40, system and programmemories 56 and 54, video encoder 80 and display controller 82 may behoused within camera control unit (CCU) 70.

CCU 70 may be responsible for powering and controlling light source 8,image sensor assembly 28, and/or optical assembly 11. In some versions,a separate front end camera module may perform some of the imageprocessing functions of image processing circuitry 30.

Although this distribution of imaging device functional control amongmultiple programmable logic devices, processors, and controllers istypical, these programmable logic devices, processors, or controllerscan be combinable in various ways without affecting the functionaloperation of the imaging device and the application of the invention.These programmable logic devices, processors, or controllers cancomprise one or more programmable logic devices, digital signalprocessor devices, microcontrollers, or other digital logic circuits.Although a combination of such programmable logic devices, processors,or controllers has been described, it should be apparent that oneprogrammable logic device, digital signal processor, microcontroller, orother digital logic circuit can be designated to perform all of theneeded functions. All of these variations can perform the same functionand fall within the scope of this invention.

As used herein the terms “comprising,” “including,” “carrying,” “having”“containing,” “involving,” and the like are to be understood to beopen-ended, that is, to mean including but not limited to. Any use ofordinal terms such as “first,” “second,” “third,” etc., in the claims tomodify a claim element does not by itself connote any priority,precedence, or order of one claim element over another, or the temporalorder in which acts of a method are performed. Rather, unlessspecifically stated otherwise, such ordinal terms are used merely aslabels to distinguish one claim element having a certain name fromanother element having a same name (but for use of the ordinal term).

The foregoing has outlined rather broadly the features and technicaladvantages of the invention in order that the detailed description ofthe invention that follows may be better understood. It should beappreciated by those skilled in the art that the conception and specificembodiments disclosed may be readily utilized as a basis for modifyingor designing other structures for carrying out the same purposes of theinvention. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the scope of theinvention as set forth in the appended claims.

Although the invention and its advantages have been described in detail,it should be understood that various changes, substitutions andalterations can be made herein without departing from the scope of theinvention as defined by the appended claims. The combinations offeatures described herein should not be interpreted to be limiting, andthe features herein may be used in any working combination orsub-combination according to the invention. This description shouldtherefore be interpreted as providing written support, under U.S. patentlaw and any relevant foreign patent laws, for any working combination orsome sub-combination of the features herein.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the invention, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to the invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

The invention claimed is:
 1. A relay system for an endoscope comprising:an opposing pair of rod lens assemblies positioned symmetrically withrespect to a central airspace, wherein each rod lens assembly includesoptical elements consisting essentially of: a meniscus lens positionedimmediately adjacent to a central airspace and with the convex surfacefacing the airspace; a first lens having positive power with a convexface positioned adjacent to the inner face of the meniscus lens, thefirst lens formed of a material having anomalous partial dispersion; arod lens, adjacent to the first lens having positive power, having afirst face and a second face, both first and second faces being beampassing faces; and an outer optical manipulating structure selected fromthe group consisting of: (i) the second face of the rod lens, beingconcave, positioned adjacent to a second lens having positive power andhaving a convex face facing the second concave face of the rod lens;(ii) the second convex face of the rod lens, being convex, positionedadjacent to an outer meniscus lens; (iii) the second face of the rodlens, being plano, positioned adjacent to a second plano convex lenshaving a convex face facing the second plano face of the rod lens with aseparation gap; and (iv) the second face of the rod lens, being convex;wherein the meniscus lens, the first lens having positive power, the rodlens, and the outer optical manipulating structure together providechromatic aberration correction by manipulating light from the blueregion of the spectrum through the near IR region of the spectrum tofollow the same sequence of optical surfaces and come to a common focusin a common image plane.
 2. The relay system of claim 1, wherein thefirst lens having positive power is plano-convex.
 3. The relay system ofclaim 1, wherein the first lens having positive optical power ismanufactured from a material having an Abbe number equal to or greaterthan
 80. 4. The relay system of claim 1, wherein the outer opticalmanipulating structure is the second, concave face of the rod lenspositioned adjacent to a second lens having positive power and having aconvex face facing the second concave face of the rod lens.
 5. The relaysystem of claim 4, wherein the second lens having positive power isplano-convex.
 6. The relay system of claim 4, wherein each rod lensassembly has no additional optical manipulating elements other than thethose listed.
 7. The relay system of claim 1, wherein the outer opticalmanipulating structure is the second convex face of the rod lenspositioned adjacent to an outer meniscus lens.
 8. The relay system ofclaim 7, wherein each rod lens assembly has no additional opticalmanipulating elements other than the those listed.
 9. The relay systemof claim 1, wherein the outer optical manipulating structure is thesecond plano face of the rod lens positioned adjacent to a plano-convexlens having a convex face facing the second plano face of the rod lenswith a separation gap.
 10. The relay system of claim 9, wherein each rodlens assembly has no additional optical manipulating elements other thanthe those listed.
 11. The relay system of claim 1, wherein the outeroptical manipulating structure is the second convex face of the rodlens.
 12. The relay system of claim 11, wherein each rod lens assemblyhas no additional optical manipulating elements other than the thoselisted.
 13. The relay system of claim 1, wherein the relay system isalso corrected for astigmatism.
 14. The relay system of claim 1, whereinthe meniscus lens is constructed of a crown glass having a refractiveindex less than 1.65 and an Abbe number between 55 and
 75. 15. The relaysystem of claim 1, wherein the chromatic aberration correction isprovided from approximately 400 nm to 900 nm.
 16. The relay system ofclaim 1, wherein the pair of rod lens assemblies is arranged around anair space containing an aperture stop.
 17. The relay system of claim 1,further comprising an endoscope containing the relay system.
 18. Therelay system of claim 1, wherein the first and second faces of the rodlens are plano.